Forget cats and dogs—it was raining spiders recently in southern Australia, according to local news reports.
Millions of spiders dropped from the sky in the Southern Tablelands region (map), blanketing the countryside with their webs. "They fly through the sky and then we see these falls of spiderwebs that look almost as if it's snowing," local resident Keith Basterfield told the Goulburn Post.
Though many news reports have called them babies, the spiders are actually just "very, very small" adults called sheet-web weavers or money spiders, according to Robb Bennett, a research associate in entomology at the Royal British Columbia Museum in Victoria.
It's unclear what spurs these spiders take to the skies in what are called mass ballooning events, Bennett notes.
But once they do, millions crawl to the highest points of their habitat—say a fence pole, or a tall plant—and send out silk strands that allow them to be lifted on air currents.
Researchers told The Sydney Morning Herald that the area may be seeing a mass migration of baby spiders. Spiders,
especially young ones, often release a stream of silk as they jump, and they can be taken with the breeze and carried away.
Mass migration can result in a large amount of what’s called gossamer or “Angel Hair,” which is the silk produced by spiders.
The astonishing spectacle usually occurs in May or August in Australia, when sunshine follows rainfall. It is rare because it requires an unusual weather pattern for this time of year, which is when spiders are hatching.
The spiderlings are light enough to float on threads, sometimes for hundreds of kilometres at up to 20,000 feet, according to Keith. They have even been spotted by aircraft.
Their long-distance travel enables them to migrate to new areas, partly for instinctual reasons and partly for food, with an increase of mosquitoes in rural areas at these times of year.
Once they land, the spiders disappear into the ground and the threads, made of protein, disintegrate until there is no evidence that anything has happened.
“Millions use this method to migrate,” said Keith. “But there are only a couple of species in Australia so it’s fairly rare to see.”
Any temperate part of Australia and other countries can experience the bizarre sight. Videos from 2013 show the flying spiders descending on Brazil and Texas, while in Denmark, researchers analysed the protein that makes up the webs to find out more.
“I’ve done historical research going back to as early as 1914 in South Australia,” said Keith. “There were about 20 falls in that time. I’m encouraging people to make videos and take photos as this is of interest to entomologists and scientists.”
"Ballooning is a not-uncommon behavior of many spiders. They climb some high area and stick their butts up in the air and release silk. Then they just take off," Vetter told Live Science. "This is going on all around us all the time. We just don't notice it."
The reason people don't usually notice this ingenious spider behavior is that it's not common for millions of spiders to do this at the same time, and then land in the same place, said Todd Blackledge, a biology professor at the University of Akron in Ohio.
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